In such a multi-stage gear, an output of the planetary gear stands in a drive connection with a wave generator of the strain wave gear. The planetary gear is arranged at least partially in a radial way within the strain wave gear.
Multi-stage gears of the category-specific type offer the advantage of a very short axial structural length while the gear has zero backlash. Pure planetary gears, however, are usually not free of backlash. Through the combination of a planetary gear with a strain wave gear, high gear reduction conditions can be achieved and high angular torques can be created. Such gears are particularly interesting for drives in the field of wheel drives and robotic applications, where both freedom of backlash as well as a high angular torque are required.
A multi-stage gear according to the generic term of the independent Claim 1 is described for example in DE 10333951 B3. In this gear, a single-stage planetary gear is used, whose planetary wheels mesh on one hand with the sun wheel and on the other hand support themselves on an internal, externally toothed support disc. The wave generator of the strain wave gear is supported exclusively on the single planetary carrier of the planetary gear.
A further multi-stage gear according to the generic term of the independent Claim 1 is known from DE 10151878 A1. Also in this gear, the wave generator of the strain wave gear is supported exclusively on the single planetary carrier of the planetary gear. The planetary wheels of the planetary gear mesh with the sun wheel and an internally toothed ring gear that is, when viewed in an axial direction, arranged next to the strain wave gear so that the overall structure of this gear is not quite as compact as in the drive from DE 10333951 B3.